In the operation of 90.degree. sweepout mechanisms for glassware forming machines of the IS type wherein a driven sprocket is coupled to the drive shaft of the sweepout through a clutching arrangement, it has been the practice in the past, as shown in U.S. Pat. No. 3,249,200, to couple the driven sprocket to the vertical shaft by means of a spring-biased detent which will release in the event the sweepout mechanism becomes jammed. It should be understood that the sprocket is driven from a cam which is rotated continuously and the follower of the cam is connected to the chain. The chain is springbiased to aid in keeping the follower riding against the cam. The mechanical portions of this drive are relatively strong and will be capable of creating damage in the upper portion of the sweepout mechanism such as breaking the sweepout fingers or the like. The detent system which is shown in some detail in FIG. 5 of the above-mentioned patent, permits the sprocket to cycle through its normal oscillations without forcing the sweepout motor to oscillate if interference with the motor is present. Once the detent is out of the hole in the sprocket, return of the detent into the hole in the sprocket must be accomplished in order for the mechanism to be capable of performing the sweepout functions. A system for assuring such return was the subject of applicant's prior U.S. Pat. No. 3,716,126 issued Feb. 13, 1973. This Perry patent shows a mechanical arrangement for rephasing the detent mechanism during the next cycle of the sprocket oscillation. The present invention is considered an improvement over this prior patent.